Diamond is a particularly useful material for forming electron emitters, because of its low work function and crystalline nature. Various methods have been proposed for forming diamond emitters. In the CVD (chemical vapor deposition) process, a gaseous carbon source at high temperature and pressure is used to deposit diamond onto a metal surface, such as of copper or nickel. It has also been proposed to use a solid carbon source at low pressure to deposit diamond onto a metal surface. A different technique is described in Journal Vacuum Science Technology, B 14(3), May/June 1996 pp 2060 to 2067. In this, a diamond grit is applied to a silicon substrate in a slurry or paste, and this is then heated in a reducing atmosphere to form electrical and mechanical contact between the diamond and silicon substrate. A layer of nickel may then be deposited on top of the diamond grit. EP-A-0718864 describes a field-emission device with diamond particles on a metal surface. Diamond is also extensively used in other applications, such as, as an abrasive.
It is an object of the present invention to provide an improved method of forming a diamond surface and a device having a diamond surface thereon.
According to one aspect of the present invention there is provided a method of forming a diamond surface comprising the steps of providing a metal surface, depositing a layer of diamond grit onto the surface and subjecting the surface and diamond grit to a gaseous atmosphere at elevated temperature, the metal surface and gaseous atmosphere being selected to cause a catalytic regrowth of the diamond grit and the metal surface being sufficiently thin that the metal surface is consumed by the treatment in the gaseous atmosphere.
The metal surface may be provided on an electrically-insulative substrate, such as selected from a group comprising silicon, quartz aluminum and glass. The diamond grit is preferably applied to the metal surface in a binder.
According to another aspect of the present invention there is provided a method of forming a diamond surface comprising the steps of providing a surface, depositing a mixture of a diamond grit and a metal powder onto the surface and subjecting the surface and deposited mixture to a gaseous atmosphere at elevated temperature, the metal powder and gaseous atmosphere being selected to cause a catalytic regrowth of the diamond grit.
The surface is preferably of an electrically-insulative material and the metal is preferably selected from a group comprising nicktel, silver, copper, titanium chromium, gold, lanthanum, cesium, magnesium, barium, aluminum and molybdenum. The diamond grit when applied preferably has a particle size in the range of a few tenths of a micron to a few microns. The gaseous atmosphere is preferably of a hydrogen-containing gas, the elevated temperature is preferably in the range 500 to 1000.degree. C. and the gaseous atmosphere preferably has a pressure in the range of a few torr to several hundred torr. The gaseous atmosphere at elevated temperature is preferably produced by a microwave plasma reactor. The diamond grit may be doped with an n-type or p-type material. The diamond grit may be produced by crushing n-type or p-type CVD diamond film.